Structural and genetic studies are in progress on kappa chain allotypes of wild rabbits. The kappa chain allotypes are so diverse in rabbits that it is of interest to determine the mechanism by which the allotypes have diverged. Hypotheses generated by examination of domestic rabbits are being tested using the additional data available from new wild rabbit allotypes which have been bred onto domestic rabbit backgrounds. Most of the amino acid sequence of allotypes b97 and b98 have been determined and nucleic acid probes for kappa chain J and C regions have been used to examine the kappa chain genes of both wild and domestic rabbit allotypes. These studies indicate similar gene arrangements and suggest gene conversion as a mechanism for allotype divergence.